1. Field of the Invention
The present invention relates to a mattress having utility in the prevention and treatment of decubitus ulcers and other tissue damage aggrevated by pressure, and/or heat, and/or shearing.
2. Related Art
Decubitus ulcers are caused by the reduction or lack of blood to skin and muscle tissue. The deprived cells quickly die and sores form. These sores often become open wounds which can spread throughout the body's soft tissue and finally expose bone mass. Predisposing conditions which contribute to the formation of decubitus ulcers include circulatory disease and the exposure of tissue to extreme temperatures, as well as shearing, i.e., friction against the skin, which can stretch and close blood vessels. A major cause of decubitus ulcers, however, is pressure.
For example, when an individual lies in a given position for an extended period of time, protrusions in the skeletal structure, such as at the back of the head, the buttocks and the heels, cause the soft tissue covering these portions of the skeletal structure to be squeezed against an underlying support surface, such as a mattress. This soft tissue is squeezed and the blood flow therein altered, and so such tissue is especially susceptible to decubitus ulcers. The position and spacing of these relatively small and localized pressure points vary from individual to individual.
Efforts have been made to design mattresses which minimize the possibility of decubitus ulcers. An example may be found in U.S. Pat. No. 3,742,528 to Munch. There, a foam frame is cemented to a rigid base and includes a central cut out. Inserts may be placed in the central cut out while other portions of the cut out are left open so that the mattress can be shaped to relieve local pressure on the body of the patient. However, this mattress cannot be used on an adjustable bed frame and the crevices created by the cut out and inserts make cleaning difficult. A person lying on the mattress will also tend to experience the uncomfortable sensation of "dropping into a hole," and the edges around the empty portions of the cut out can create a "cookie cutter effect" on portions of the patient lying thereon as the body presses against the mattress surface. Another source of discomfort is derived from the relatively high friction coefficient of the foam mattress which tends to shear against a patient's skin as the patient descends into the mattress.
U.S. Pat. No. 3,146,469 to Slade also discloses a mattress having cut outs for conforming to a body shape, in order to reduce the possibility of bed sores. There, a mattress is mounted on a plurality of wooden slats and is made of a foam material entirely encased by waterproof vinyl. Cut outs in the mattress may be filled with correspondingly shaped blocks. However, this mattress does not reduce heat build-up, which increases the susceptibility of skin damage or breakdown. Moreover, the cleaning, comfort and shear problems associated with Munch will also arise in Slade.